1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor element, which employs contact hole opening with the use of a femtosecond laser. The present invention also relates to a method for manufacturing a semiconductor device that includes a semiconductor element.
2. Description of the Related Art
In a thin film transistor (hereinafter also referred to as a TFT) and an electronic circuit using the thin film transistor, various thin films such as a semiconductor film, an insulating film, and a conductive film are stacked over a substrate, and they are appropriately processed to have predetermined contact holes by a photolithography technique. The photolithography technique is a technique in which a pattern of a circuit or the like which is formed over a transparent flat plate by using a material that does not transmit light, which is referred to as a photomask, is transferred to a target substrate by using light. The photolithography technique is widely used in a manufacturing process of a semiconductor integrated circuit and the like. Then, a contact hole can be formed in a desired position by removing a part of an insulating film, a semiconductor film, a metal film, or the like in a portion to be a contact hole while using, as a mask, a pattern which is transferred to a substrate by a photolithography technique.
The conventional manufacturing process using the photolithography technique requires multiple steps such as exposure, development, baking, and peeling only for treating a mask pattern formed by using a photosensitive organic resin material that is also referred to as a photoresist. Therefore, the manufacturing cost is inevitably increased as the number of photolithography steps is increased. In order to solve this problem, it has been attempted to manufacture TFTs through a smaller number of photolithography steps (Reference 1: Japanese Published Patent Application No. 2000-133636). In Reference 1, a resist mask formed through a photolithography step is used once and is then reused as a resist mask having a different shape by expansion in its volume by swelling.